MDL-79174 availability: Allow group condition to use hidden groups

Previously, groups with GROUP_VISIBILITY_NONE could be selected for an
availability condition, but as the group API did not return a user's own
groups with this visibility, the condition's is_available check always
failed.

This change uses the new $includehidden parameter to get all of a user's
groups from groups_get_user_groups when evaluating the condition, so
these groups work as expected. Due to the enforced hiding of conditions
containing these groups, they will never be seen by the user.

availability/condition/group/classes/condition.php

@@ -71,7 +71,7 @@ class condition extends \core_availability\condition {
         $allow = true;
         if (!has_capability('moodle/site:accessallgroups', $context, $userid)) {
             // Get all groups the user belongs to.
-            $groups = $info->get_modinfo()->get_groups();
+            $groups = $info->get_groups();
             if ($this->groupid) {
                 $allow = in_array($this->groupid, $groups);
             } else {